The overall goal of this study is to identify RA susceptibility genes that lie outside the Major Histocompatibility Complex. This project is being conducted by a consortium of investigators at ten sites across the U.S., including UCSF. A total of 1,000 sibling pairs with rheumatoid arthritis, plus available parents, will be enrolled at these sites. One hundred fifty sib pairs will be enrolled at the UCSF site, under the direction of Dr. Criswell. The GCRC will be used to perform the required enrollment procedures. In brief, Dr. Criswell will meet study participants at the GCRC where she will perform a physical examination. GCRC staff will assist with questionnaire administration, phlebotomy, and coordination of performance of hand x-rays at the Moffitt Radiology Department. Blood samples will be shipped from the GCRC to the North Shore University Hospital, the central processing site for specimens.